Numerous attempts have been made to obtain artificial membranes which can be used as substitutes for skin, blood vessels, ligaments, or other connective tissue. Many of these membranes utilize collagen, as collagen is the major component of connective tissue in general. An extensive literature exists with respect to methods for preparing such membranes, either of collagen alone, (see, for example, U.S. Pat. No. 4,412,947; Japanese Pat. No. 74/039174; and U.S. Pat. No. 4,242,291) or of collagen in combination with other materials (see, e.g., U.S. Pat. No. 4,453,939). Other membranes use combinations of materials such as glycoproteins with fibrinogen and thrombin (EPO Application Publication No. 92200, published Oct. 26, 1983), and a combination of keratin derived and glycosaminoglycan polymers (European Patent Publication No. 89152, published Sept. 21, 1983).
The properties and quality of the resulting membranes with respect to physical characteristics useful in the particular application intended, and their biological characteristics, such as biocompatibility, stability, and integration with surrounding tissue are determined by the nature of the material, e.g., the nature of the collagen used to form the membranes, and on the process used in their formation.
The membranes in the art have had variable success for their intended uses, which include cornea replacements, artificial skin, and wound healing. Many cause inflamation, and have less than optimum properties of flexibility, biological stability, and strength.
The present invention offers a process whereby desirable properties can be obtained in the resulting membrane through the use of nonimmunogenic collagen formed into a membranous material by a spectrum of processes which offer flexibility in the physical properties of the product, so as to permit these properties to be adapted to intended use. The membranous material can be used as a two-dimensional membrane, including membranes which can be shaped to form tubular vessels, shaped into a three-dimensional implant, or formed into a one-dimensional fiber.